1. Field of the Invention
The invention relates to a hydroelectric power generating device submerged in relatively slow moving water, as in a river or tidal basin. Keeping the device in an optimal water channel velocity during tidal cycles, as well as propeller and shaft orientation with respect to water channel flow are the chief design goals for maximizing the generating capacity factor in a river or tidal basin.
2. Description of the Prior Art
Power generation efficiency within a natural and variable medium requires that the turbine propeller maintain a perpendicular relationship to the water's direction. Past examples of river or tidal basin energy conversion devices have depth and level control in moving water that is regulated by the system's fore and aft wings. Using a system of wings for control is only effective in a dynamic environment—action and reaction. When water is at standstill no control is possible, necessary leveling and depth control is not achieved and bottoming can occur. Other tethered devices have characteristics which prevent bottoming, but are fixed in one direction, and cannot yaw to face water from opposite directions, as in a tidal basin. Additionally, tethered devices that sense only depth are not suited to tidal basin installation, as the depth, which is measured from the water surface, will vary during tidal cycles, while the elevation, which is measured from the seabed, will not. Another past approach utilized with some success is a fixed suspension from a bridge or piling or some other structural means of support. This fixed arrangement fails to satisfy the desired requirement for maximum efficiency due to its inability to maintain a perpendicular relationship to the water's direction. A fixed system precludes the elevation adjustment necessary in an open water channel. As water velocity and surface level varies due to seasonal or tidal change—a fixed system can not adjust. Fixed suspension also precludes the realization of an optimum maximum device capacity factor (ratio of actual kilowatt-hours generated—for the time considered, to the kilowatt-hours that could have been generated at continuous full power operation during the same time period). The vertical freedom of movement for any open channel energy conversion device is acutely necessary to realize a maximum generation capacity factor. What is needed is a tethered, submerged power generating device which is free to traverse up and down in elevation and yaw to orient the turbine propellers perpendicular to water flow in an environment with reversing water flow conditions.